Re: [PATCH v8 0/5] MT8196 GPU Frequency/Power Control Support

Ulf Hansson
2025-10-22T13:53:29Z

On Fri, 17 Oct 2025 at 17:32, Nicolas Frattaroli
<nicolas.frattaroli@collabora.com> wrote:
>
> This series introduces two new drivers to accomplish controlling the
> frequency and power of the Mali GPU on MediaTek MT8196 SoCs.
>
> The reason why it's not as straightforward as with other SoCs is that
> the MT8196 has quite complex glue logic in order to squeeze the maximum
> amount of performance possible out of the silicon. There's an additional
> MCU running a specialised firmware, which communicates with the
> application processor through a mailbox and some reserved memory, and is
> in charge of controlling the regulators, the PLL clocks, and the power
> gating of the GPU, all while also being in charge of any DVFS control.
>
> This set of drivers is enough to communicate desired OPP index limits to
> the aforementioned MCU, referred to as "GPUEB" from here on out. The
> GPUEB is still free to lower the effective frequency if the GPU has no
> jobs going on at all, even when a higher OPP is set.
>
> The power- and frequency control driver, mtk-mfg-pmdomain, is now
> implemented as a power domain driver, with a set_performance_state
> operation. It also exposes itself as a clock provider, so that panthor
> can read the actual achieved DVFS clock rate as per the GPUEB firmware.
>
> This power domain approach means that panthor does not need to know
> about how the frequency control works on this SoC, as the OPP core
> framework already takes care of it. The only exception is that panthor
> needs to not register OPPs from DT itself if there already is an OPP
> table present.
>
> The mailbox driver is a fairly bog-standard common mailbox framework
> driver, just specific to the firmware that runs on the GPUEB. It was
> merged in v6.18 already.
>
> Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>

This looks good to me!

I can certainly pick up patch2 and patch5, but before I go ahead I
just wanted to check what is the preferred merging strategy?

The drm/gpu patches can go independently from the pmdomain patches
others, right? In either case, I can pick this complete series too via
my pmdomain tree, if that makes sense for everyone. Please let me
know.

Kind regards
Uffe

> ---
> Changes in v8:
> - mtk-mfg-pmdomain: remove unused shmem variable that caused a warning
> on GCC, but not clang
> - Link to v7: https://lore.kernel.org/r/20251015-mt8196-gpufreq-v7-0-0a6435da2080@collabora.com
>
> Changes in v7:
> - panthor: rename "t" to "table"
> - panthor: add code comment explaining why an existing OPP table is
> being checked for
> - mtk-mfg-pmdomain: use GF_REG_MAGIC offset for sake of consistency
> - mtk-mfg-pmdomain: remove redundant semicolon after mtk_mfg_mt8196_init
> - mtk-mfg-pmdomain: fix resource leaks on probe failure
> - mtk-mfg-pmdomain: enable/disable EB clock during MT8196 init, which is
> needed for the register read
> - Rebase onto next-20251014, which drops already merged patches, namely
> mailbox driver+bindings, and drops the ASN_HASH patch series
> dependency, which was also merged
> - Link to v6: https://lore.kernel.org/r/20251003-mt8196-gpufreq-v6-0-76498ad61d9e@collabora.com
>
> Changes in v6:
> - mailbox: move buf definition into if condition, as per Chia-I Wu
> - panthor: remove the redundant NULL checks in panthor_devfreq_get_freq
> - mtk-mfg-pmdomain: adjust return style consistency
> - mtk-mfg-pmdomain: add docstring for mtk_mfg_send_ipi to explain it's
> blocking
> - mtk-mfg-pmdomain: use CMD_FIX_DUAL_TARGET_OPPIDX instead of
> CMD_FIX_TARGET_OPPIDX.
> - mtk-mfg-pmdomain: reword code comments to not be in the "we" style
> - mtk-mfg-pmdomain: shuffle around mbox allocations as per Angelo
> - mtk-mfg-pmdomain: don't pointlessly turn on EB clock in probe,
> reducing the need for a comment explaining the bookkeeping
> - mtk-mfg-pmdomain: consistently use dev_err_probe and Capitalise first
> letter of error string
> - mtk-mfg-pmdomain: get rid of redundant ret = dev_err_probe assignment
> - mtk-mfg-pmdomain: reintroduce stack OPP table, choose min(gpu, stack)
> when adding frequencies. Fixes gaps in OPP levels where only stack
> changed, but gpu had duplicates, which resulted in choosing a too slow
> OPP
> - mtk-mfg-pmdomain: stub round_rate clk op to opt out of CCF always
> "rounding" a devfreq rate request to the current rate
> - Link to v5: https://lore.kernel.org/r/20250929-mt8196-gpufreq-v5-0-3056e5ecf765@collabora.com
>
> Changes in v5:
> - mtk-mfg-pmdomain binding: add memory-regions property, remove shmem
> property, as we now correctly describe the shared memory as a regular
> memory region
> - mtk-mfg-pmdomain binding: get rid of redundant |
> - drop "dt-bindings: sram: Add compatible for
> mediatek,mt8196-gpufreq-sram" as part of the move to reserved memory
> - mtk-mfg-pmdomain: move to using reserved-memory for GPUEB shared
> memory
> - mtk-mfg-pmdomain: demote some types to smaller sizes in struct
> mtk_mfg, as per Angelo's suggestions
> - mtk-mfg-pmdomain: use units.h for Hz-to-KHz
> - mtk-mfg-pmdomain: change for loop in attach_dev to reduce indentation
> - mtk-mfg-pmdomain: simplify return in mtk_mfg_power_off
> - mtk-mfg-pmdomain: move of_device_id after probe
> - mtk_mfg_pmdomain: map mmio by index
> - mtk_mfg_pmdomain: add error checking to pm_genpd_init()
> - mtk_mfg_pmdomain: add remove function
> - mtk_mfg_pmdomain: remove last_opp member and logic, since OPP core
> already does that for us
> - mtk_mfg_pmdomain: adjust comment in mtk_mfg_set_performance to explain
> why we're doing what we're doing
> - mtk_mfg_pmdomain: call mtk_mfg_set_oppidx in mtk_mfg_power_on with
> the performance_state we deferred setting while it was powered off
> - mtk_mfg_pmdomain: add inline function for PWR_ACK checking, as it's
> now used twice with the added remove function
> - mtk-mfg-pmdomain: add suppress_bind_attrs so people don't play with
> that
> - mtk-mfg-pmdomain: change KConfig from tristate to bool, as module
> unloading results in strange likely firmware-induced hardware state
> woes in the mali GPU
> - mtk-mfg-pmdomain: read IPI magic in power_on, don't zero it after
> confirming that seemingly had no purpose
> - mtk-mfg-pmdomain: misc style changes
> - Link to v4: https://lore.kernel.org/r/20250923-mt8196-gpufreq-v4-0-6cd63ade73d6@collabora.com
>
> Changes in v4:
> - rebase onto next-20250922, which includes Laura Nao's clock patches
> - refactor mediatek_mfg into a pmdomain driver called "mtk-mfg-pmdomain"
> - move mt8196-gpufreq binding to the power subdirectory
> - mali-valhall-csf binding: adjust for power-domains usage
> - mali-valhall-csf binding: use clocks on mt8196
> - mailbox: prefix defines with "GPUEB_"
> - mailbox: get rid of custom of_xlate
> - mailbox: rename "CLOGGED" to "BLOCKED"
> - mailbox: adjust send_data comment to include more technical info
> - mailbox: misc style improvements
> - panthor: drop "drm/panthor: devfreq: make get_dev_status use
> get_cur_freq", as it is now not necessary and makes the code worse
> - panthor: drop "drm/panthor: devfreq: add pluggable devfreq providers"
> - panthor: drop "drm/panthor: add no_clocks soc_data member for MT8196",
> as we now have clocks courtesy of gpufreq
> - panthor: check for existing opp table before registering a new one
> - mtk-mfg-pmdomain: add turbo_below variant data, which marks OPPs below
> a certain index as turbo for the OPP subsystem
> - mtk-mfg-pmdomain: no longer read stack OPPs, as they weren't used
> - mtk-mfg-pmdomain: get rid of num gpu opp != num stack opp check.
> That's the firmware's problem should it ever happen, not ours
> - mtk-mfg-pmdomain: some small name and whitespace changes on the defines
> - Link to v3: https://lore.kernel.org/r/20250917-mt8196-gpufreq-v3-0-c4ede4b4399e@collabora.com
>
> Changes in v3:
> - mali-valhall-csf binding: get rid of clocks for MT8196, rebase onto
> Chia-I Wu's patch
> - mt8196-gpufreq binding: rename hw_revision to hw-revision
> - mt8196-gpufreq binding: rename clocks
> - mt8196-gpufreq binding: drop pointless label in example
> - mailbox binding: drop pointless label in example
> - mailbox: whitespace changes on defines
> - mailbox: remove rx_buf member from channel struct, use stack buffer
> - mailbox: check in probe that no rx_len exceeds MBOX_MAX_RX_SIZE
> - panthor: add no_clocks SoC data patch, also rebase onto Chia-I Wu's
> series
> - panthor: refactor devfreq provider functionality to do allocation and
> initialisation of panthor_devfreq struct in panthor in all cases
> - panthor: drop the patch that moves struct panthor_devfreq to a header
> file, as it no longer needs to be exposed to devfreq providers
> - mediatek_mfg: refactor devfreq provider functionality to decouple it
> more from panthor itself
> - mediatek_mfg: move SRAM magic to a #define
> - mediatek_mfg: begrudgingly rename member "padding_lol" to "reserved"
> - mediatek_mfg: use local struct device pointer var in more places
> - mediatek_mfg: change wording of sleep command failure error message,
> but keep the format specifier because I don't want to throw bare
> errnos at users
> - mediatek_mfg: remove unnecessary braces around dev_err EB power off
> timeout message
> - mediatek_mfg: allocate rx_data for channels that expect a response
> - mediatek_mfg: memcpy the rx buffer from the common mailbox framework
> in the rx callback to rx_data, as mssg now points to stack memory
> - mediatek_mfg: make SRAM clearing message dev_dbg
> - mediatek_mfg: no longer print physical address of SRAM
> - mediatek_mfg: expand on the GF_REG_OPP_TABLE_STK comment, toning down
> its defeatist attitude in the process
> - mediatek_mfg: style fixes in mtk_mfg_get_closest_opp_idx
> - mediatek_mfg: rename clocks and hw-revision reg as per binding
> - Link to v2: https://lore.kernel.org/r/20250912-mt8196-gpufreq-v2-0-779a8a3729d9@collabora.com
>
> Changes in v2:
> - mali-valhall-csf binding: move from performance-controller to
> performance-domains property
> - mali-valhall-csf binding: fix vendor name oopsie in compatible of if
> condition
> - mt8196-gpufreq binding: move from performance-controller to
> performance-domains by adding the cells property
> - mt8196-gpufreq binding: rename e2_id to hw_revision
> - mt8196-gpufreq binding: add description that mentions "MediaTek
> Flexible Graphics"
> - mt8196-gpufreq binding: get rid of mailbox channels we're unlikely to
> use any time soon, if ever
> - mt8196-gpufreq binding: change name of mailbox channels to use -
> instead of _
> - mailbox binding: change reg-names to "data" and "ctl"
> - drm/panthor: mediatek_mfg: rename e2_id to hw_revision
> - drm/panthor: devfreq: switch from performance-controller to
> performance-domains
> - drm/panthor: devfreq: get rid of the accidental get_cur_freq function
> move
> - mailbox: rename mtk_gpueb_mbox_ch to mtk_gpueb_mbox_chan_desc
> - mailbox: use smaller types in mtk_gpueb_mbox_chan_desc where possible
> - mailbox: add per-channel runtime data struct
> - mailbox: request one threaded IRQ per channel, pass channel struct as
> data
> - mailbox: make num_channels in variant struct u8
> - mailbox: get rid of no_response, as it was redundant
> - mailbox: enable and disable clock in mailbox startup/shutdown
> - mailbox: point con_priv of mailbox framework channel struct to this
> driver's channel struct
> - mailbox: request and free the threaded IRQ in startup/shutdown
> - mailbox: only clear IRQ bit flag once RX data has been read from MMIO
> - mailbox: reduce needlessly large receive buffer size
> - mailbox: handle allocation errors wherever they could pop up
> - mailbox: style cleanups in mtk_gpueb_mbox_read_rx
> - mailbox: call platform_get_irq earlier on in probe
> - mailbox: set drvdata later on in probe
> - mailbox: ioremap resources by index, not name
> - mailbox: handle devm_mbox_controller_register errors
> - mailbox: rename channels to correspond to bindings
> - mailbox: document a few of the private driver structs to be kind to
> the next person who will look at this code
> - Link to v1: https://lore.kernel.org/r/20250905-mt8196-gpufreq-v1-0-7b6c2d6be221@collabora.com
>
> ---
> Nicolas Frattaroli (5):
> dt-bindings: gpu: mali-valhall-csf: add mediatek,mt8196-mali variant
> dt-bindings: power: Add MT8196 GPU frequency control binding
> drm/panthor: call into devfreq for current frequency
> drm/panthor: Use existing OPP table if present
> pmdomain: mediatek: Add support for MFlexGraphics
>
> .../bindings/gpu/arm,mali-valhall-csf.yaml | 37 +-
> .../bindings/power/mediatek,mt8196-gpufreq.yaml | 117 +++
> drivers/gpu/drm/panthor/panthor_devfreq.c | 62 +-
> drivers/gpu/drm/panthor/panthor_devfreq.h | 2 +
> drivers/gpu/drm/panthor/panthor_device.h | 3 -
> drivers/gpu/drm/panthor/panthor_drv.c | 4 +-
> drivers/pmdomain/mediatek/Kconfig | 16 +
> drivers/pmdomain/mediatek/Makefile | 1 +
> drivers/pmdomain/mediatek/mtk-mfg-pmdomain.c | 1044 ++++++++++++++++++++
> 9 files changed, 1268 insertions(+), 18 deletions(-)
> ---
> base-commit: 3477f49ff0433a241da12ec9cecf6c9b2bd1c6f8
> change-id: 20250829-mt8196-gpufreq-a7645670d182
>
> Best regards,
> --
> Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
>